Pickup for detecting and translating vibrations



Feb. 16, 194-3. G L HAL 2311,41

PICKUP FOR DETECTING AND TRANSLATING VIBRATIONS- I Original Filed July 17. 1939 My f? Patented Feb. 16, 1943 PICKUP FOR DETECTING AND TRANSLAT- ING VIBRATIONS Oscar G. Salb, Indianapolis, Ind., and Ralph E. Sturm, Milton, Wis.

Original application July 17, 1939, Serial No.

285,028. Divided and this application January 6, 1941, Serial No. 373,238

2 Claims.

Our invention relates to pick-ups for detecting and translating vibrations-in other words to an instrument which is affected by vibratory movements and converts the same into electrical phenomena, e. g., e lectrical waves.

It will be shown and described as embodied in an instrument particularly adapted to detect, at the chest wall, vibrations emanating from the heart, and translating them into corresponding electrical waves which may be amplified and converted into visual indications by such equipment as set forth in our application Serial No. 285,028, filed July 17, 1939-01? which application this application is a division.

One of the objects of our invention is to provide an improved pick-up.

Another object is to provide a pick-up which will respond reliably to heart vibrations which are both within and without the audible frequency ranges.

Another object is to provide a pick-up which will be unaffected by variations in the pressure at which it may be applied to the chest wall.

A further object is to provide a pick-up which will be sensitive to vibrations of low magnitude and frequency but insensitive to extraneous disturbances.

Other objects and advantages will hereinafter appear.

In the drawing:

Fig. 1 is a vertical mid cross-section;

Fig. 2 is a front view, and

Fig. 3 is a plan of one of the supporting or suspension elements for the movable coil and chestcontact button.

The pick-up is designated generally at I5 and comprises a protective casing I 45 having therein a permanent magnet 95 with poles 96 and 91. Suspended in the air gap between these poles is a coil 98 carried by a cylindrical form 99 to which is attached in a suitable manner, such as by cement, a body contact button I00. This button I00 may be made of any suitable material, such as metal or artificial resins, and should be of light weight.

7 in the air-gap between poles 96 and 91.

Button I00, coil form 99 and coil 98 are connected in any suitable manner to flexible supporting spider members I 0| and I02 which are attached firmly by layers of rings I03 and I04 to the pole piece 96. Over the complete assembly, with an aperture having a slight clearance for button I00, there is placed a cover member I05 which may be of any resilient material such and in order to minimize the vibrations due to skinfriction an annular bead I06 is provided. This bead will form contact with the chest skin surrounding button I00 and prevent relative motion between this skin and the housing of the pickup. Such motions might otherwise cause extraneous vibrations to be detected and trans-' mitted to the viewing screen of cathode ray tube 2|.

Detector or pick-up I5 is of the electro-dynamic coil type and vibrations detected through button I00 cause coil 98 to move across the field set up The voltage generated in coil 98 is taken ofi by suitable leads (not shown). Spider members IM and I02 are made of extremely thin material and may be of metal, paper, or one of the artificial resins such as Bakelite. As shown in Fig. 3, these members have arms I01 projecting inwardly from an annular portion I08 at the outer periphery of spider members IM and I02, and form into a central annular portion 0. The supporting arms are elongated by providingeach with a portion extending over an appreciable arc and concentric with the annular portions I 08 and 0. By so forming supporting arms I01 they can be made of considerably greater length than the straight radial distance between annular por-f tions I08 and II 0, and will afford greater flexibility to the entire supporting spider. Thus, the body contact member can travel for a considerable distance without substantially stretching the material of the spider member or without undue resistance to movement thereof.

Further, this construction of the spider member minimizes the pick-up of vibrations other than those desired as it presents 'a small area outside of the body contact member I00 upon which vibrations can impinge. Spider members IOI and I02, therefore, do not act as the diaphragms of an acoustic pick-up, but form a supporting member for holding the coil 98 in the air gap and for permitting the travel of the body contact member to an appreciable distance without undue stress of the material of the spider members. These spider members may be made of any suitable material. For example, an extremely satisfactory pick-up has been made in which the spider members are of fiat Bakelite of .015 inch in thickness and wherein button I00 is composed of Bakelite, machined or molded, with a thickness of .005 inch.

Having thus illustrated and described the naas rubber. Detector I5 is extremely sensitive ture of an embodiment of our invention, what we claim and desire to secure by United States Letters Patent is as follows:

1. In a dynamic type pick-up having a magnetic field and a coil positioned in said field so that vibrations of the coil produce electrical impulses through the coii, the combination comprising a portion of resilient vibration damping material having a raised chest-wall engaging rim and a recessed central web having a relatively small centrally located hole therethrough, a body contact button slightly smaller thanthe hole passing therethrough said button being spaced substantially fromvsaid rim and having a head of small area positioned in approximately the same plane as the crest of the rim, said button being aillxed-to the coil so that all vibrations of the button will produce corresponding vibrations of the coil, and resilient means for supporting the button and the coil.

2. In a dynamic type pick-up, for detecting chest wall vibrations,"having a magnetic field and having a coil positioned in the magnetic field so that movements of the coil produce elecother.

tric impulses. the combination comprising a supporting portion of resilient vibration absorbative material; for supporting the pick-up, having a raised'chest wall engaging rim and having a recessed central web portion having a hole or small cross sectional area therethrough, a chest wall contact button slightly smaller than said hole, extending freely therethrough into approximately the same plane as the apex oi the rim, said button being spaced substantially from said rim. and being rigidly connected with said coil so that all vibrations of said button are transmitted to said coil and an annular spider having a central portion supporting said coil and said button, said spider being supported at its outer margin and having a plurality of arms extending from the outer portion of the spider to the central portion thereof, each arm being constructed and disposed so that its inner and outer extremities are angularly displaced from each OSCAR G. SALB. RALPH E. STURM. 

